Convert Website Design Details into CSS Custom Properties

Convert website design details into CSS custom properties by first grouping the observed values into colors, typography, spacing, shape, and elevation, then naming each value by its interface role. Keep the exported variables as an observed reference, and validate them against the page before treating them as your project's official design system.

Start with roles, not raw values

Begin with a small semantic set that explains how each value is used. For example, use --color-background, --color-surface, --color-text, --color-text-muted, --color-border, --color-accent, and --color-focus instead of names such as --gray-100 or --blue-500. Role-based names make the CSS easier to maintain when the design changes or when the same interface needs a dark theme.

Organize the rest of the variables around the decisions a developer needs to make: --font-body, --font-heading, --font-size-sm, --font-size-body, --font-size-xl, --line-height-body, --space-1 through --space-6, --radius-sm, --radius-md, --shadow-sm, and --shadow-lg. You do not need to export every measured value. Preserve repeated values and values that clearly control a shared component, then leave one-off details for the component stylesheet.

Turn observations into usable CSS

A practical starter file might look like this:

Use the variables in component rules rather than copying values into each selector. Add fallbacks when the exported font or color may not load, and define a separate [data-theme="dark"] or @media (prefers-color-scheme: dark) block only when the reference provides enough evidence for a second theme. The examples below show a compact sans-serif treatment for Linear, with Inter used for body text and emphasized interface text. Borrow the structure as a starting point, then verify the values against your own capture.

Check the result before shipping

Compare the generated variables with the source page in the states that matter: the main screen, a dense component such as navigation or a table, a form control, and a narrow viewport. Check whether text remains readable, whether muted text is intentionally subdued rather than accidentally low contrast, and whether spacing still creates the same grouping between labels, controls, and content.

Then test the variables in a small component set: a page shell, heading and paragraph, button, input, card, and alert. If several components need exceptions, the naming may be too literal or the extracted details may be mixing different page sections. If one variable appears everywhere, keep it semantic and stable. If a value is only visible in one decorative illustration, keep it local instead of promoting it to a global property.

Remember that extracted details describe what was observed on a website. They do not prove ownership of the site's internal design system, source tokens, hidden states, or design files. Treat the CSS as a working reconstruction, document the page and state it came from, and have a designer review the result before making it a shared foundation.

Use this in your AI agent

> Inspect the captured website reference and convert its observed colors, typography, spacing, borders, radii, shadows, and gradients into a semantic CSS custom property file. Group variables by role, include sensible font fallbacks, separate light and dark values only when supported by the reference, and provide a short mapping from each variable group to the page elements where it appears. Clearly label observed values as reconstructed details rather than an official internal design system. Use the examples below as visual references, then return the CSS and a validation checklist. > > Install Fudge for your AI agent

Use two layers: a small palette layer for reusable values and a semantic layer that maps those values to interface roles. The palette layer can contain names such as --gray-100, --gray-700, or --indigo-500, while the semantic layer maps them to decisions such as --color-background, --color-text, --color-border, and --color-accent.

For example:

This keeps the measured palette available without forcing components to understand raw color names. If two grays look similar but serve different jobs, give them separate semantic names because they may change independently. For accessibility, check text and control combinations after assigning roles rather than relying on color names alone.

Copyable prompt: Ask Fudge to group the reference colors into a small palette and semantic CSS variables, explain each mapping, and flag any contrast decisions that need review. Use Fudge with your AI agent

Include the values that help another developer rebuild common page elements consistently. A useful export usually contains background and surface colors, text and muted text colors, borders, accents, focus states, font families, font sizes, weights, line heights, spacing steps, radii, shadows, and any repeated gradients. Add component mappings when the same variables appear in buttons, cards, navigation, forms, or alerts.

Keep the export readable and split it into sections such as colors, typography, spacing, shape, elevation, and components. Include source notes outside the CSS or in comments: the captured page, the viewport or state reviewed, and whether a value was directly observed or chosen as a fallback. That distinction prevents a reconstructed value from being mistaken for an official token.

Before sharing the file, load it in a test page, check the main layout and a dense component, resize the viewport, test keyboard focus, and compare the result with the reference. Remove unused variables and collapse duplicates only after confirming that the values serve the same role. A smaller, clear theme is more useful than a long list of measurements with no usage context.

Copyable prompt: Ask Fudge to export the captured website's reusable colors, type, spacing, borders, radii, shadows, and gradients as organized CSS custom properties with source notes and a validation checklist. Use Fudge with your AI agent

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